Tuesday marked the 70th anniversary of the liberation of the Auschwitz concentration camp in Nazi occupied Poland. By the time the Russians reached the camp in early 1945, more than 1.5 million souls had perished inside the walls of the German death camp — one of several such facilities constructed by Germany during World War II to carry out the Nazi’s “Final Solution” to rid the world of those they deemed “undesirable.”

It is important that we remember the Holocaust for the 11 million lives that were taken in the Nazi’s genocide machine. It is also critical that we ensure current and future generations are taught both the history of the Holocaust, as well as the lessons that allowed one of humanity’s worst atrocities to take place.

What is alarming is that nearly seven decades following the liberation of the first Nazi death camp, a major poll conducted in 2014 showed that 54 percent of the respondents had never heard of the Holocaust. When we fail to learn the lessons of the past, humanity has proven time and again our propensity to make the same mistakes over and again.

In 1978, I was a high school student in West Germany, where my father was serving in the U.S. Army. My father understood the importance of learning from the past. During the three years my family lived in Germany, my father insisted we visit as many historical sites as we could. In the summer of 1978, Dad felt it was important for my sister and I to see Dachau, the Nazi death camp located in northern Munich.

For as a long as I live, I will never forget that experience. Unlike most of the other Nazi concentration camps that were burned to the ground by liberating forces to prevent the spread of disease, the American forces liberating Dachau chose to preserve the camp as both a memorial to those who perished and a museum documenting the atrocities committed within its walls.

Walking up to the compound, I was immediately struck by the words “Arbeit Macht Frei” (work will set you free) shaped in wrought iron in the entry gates to the camp. For most of Dachau’s existence from 1933-1945, it was used as a slave labor camp for the Nazi war machine. Before even walking through those gates, my thoughts turned to all those souls who had arrived decades before, having been stripped of everything they own and told if they worked hard, they would be set free.

It was a lie.

Walking through those gates into the compound, more than 30 years after the furnaces had been permanently silenced, my nostrils burned from a horrendous odor that I had never smelled before. I asked my dad what it was. When he told me, my knees nearly buckled. “It’s from the crematoriums,” he said. “That’s what the burning of human flesh smells like.”

Toward the latter years of the war, Dachau was expanded from a slave labor camp for political prisoners to include an expanded role in Hitler’s Final Solution to exterminate the Jews. In order to facilitate the mass genocide, gas chambers were constructed, along with rows and rows of crematoriums to dispose of the bodies. From the information displayed on the walls of the museum, the crematoriums were in operation 24/7 unable to keep pace with the Nazi death machine, as mounted photos on the wall displayed mounds of emaciated bodies awaiting the ovens.

All these years later, I can still remember that smell.

After walking through the wrought iron gates, Nazi SS officers decided which of the new arrivals would be sent to the work camps, as well as those deemed worthy for the medical experiments that were being conducted. Those not chosen were sent directly to the gas chamber.

It was a surreal, humbling experience.

Near the end of the tour, my father made sure to point out a display depicting how U.S. Brigadier General Henning Linden forced civilians in the neighboring town to march through the camp following its liberation — to ensure they knew what actions their government had committed in their name.

It was difficult to believe that so many people could have turned a blind eye to the Holocaust. I still have difficulty understanding how an entire nation could have allowed their government to commit such atrocities. How could they not know? Why didn’t the people speak up and say this is wrong? Why did the German people allow this to happen? I was stunned by the reactions of the German citizens who claimed they had no idea their government was murdering hundreds of people every day just a few blocks from where they lived. What did they think happened to the Jews when the government seized their property and their families loaded on trains as they were banished from their community?

Before my father’s tour in Germany ended and we returned to the States, we also visited the Bergen-Belsen concentration camp in Northern Germany. It is the camp where Anne Frank was killed. Liberated by the British, the camp was burned to the ground to try and contain the disease that was rampant among the survivors. The site has been preserved as a memorial and there is a museum with photos showing the condition of the camp when the British liberated it.

I remember being taken aback by the mounds of mass graves located throughout the site, each containing the remains of several hundred unidentified souls. Looking at the photos in the museum, my heart ached at seeing the images of life inside the camp, realizing that for most, it marked their final days on this earth.

Humans are a very complex species. We are capable of accomplishing great endeavors as well as carrying out acts of compassion and generosity to those in need. On the opposite side of the coin, we are also a most violent species. Our history is filled with acts of brutality, war and genocide.

Whether committed for the purpose of national supremacy, religious intolerance, greed, fear or outright racism, we cannot allow ourselves to rationalize those acts by believing just because they were committed in the past, they will never happen again.

And for those who think such atrocities could never happen here, I strongly urge you to study American history. For much of the 19th century, in the name of Manifest Destiny, the American government carried out a systematic plan of cultural genocide against Native Americans. For more than a century following the American Civil War, several state and local governments passed and enforced laws designed to oppress African-Americans. During World War II, Americans of Asian decent, specifically of Japanese heritage, were removed from the homes and placed in detention camps without due process. While we are found of proclaiming ourselves as the beacon for freedom and democracy, the historical record clearly shows our government’s hands are not entirely clean when it comes to claiming the high moral ground. And as I studied the historical accounts, so many questions came to mind. Much like I did on that summer’s day in 1978 when I stood in the center of an evil place called Dachau and questioned the German people for being complaisant during the Holocaust, I asked myself how could we could have stood by silently, believing any of these acts were alright? I also knew if it happened once, it could certainly happen again.

In the seven decades since the liberation of Auschwitz, similar atrocities against humanity have happened, and it continues to happen today. It has happened in Bosnia, in Africa, in Iraq and is happening right now throughout much of the Middle East. It doesn’t matter what label we put on it or what cause is used to justify denying the liberty and life of others based on ethnic, racial or religious grounds. It is still wrong. We, as members of the human race, have an obligation to speak out in a unified voice declaring we will not let this happen ever again.

We must remember. Otherwise, humanity will be doomed to continue making the same mistakes again and again.